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Classification of microbes (and other living things)

Classification of microbes (and other living things). Major events in the history of life: life was originally microscopic and unicellular. Taxonomy: the science of naming and classifying organisms (Carolus Linnaeus) Phylogeny: evolutionary history

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Classification of microbes (and other living things)

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  1. Classification of microbes (and other living things)

  2. Major events in the history of life:life was originally microscopic and unicellular

  3. Taxonomy: the science of naming and classifying organisms (Carolus Linnaeus) Phylogeny: evolutionary history Systematics: the science of classification based on evolutionary history of organisms

  4. Linnaean classification system is used today (with modifications) • Binomial (“scientific name”) • Genus and species names (specific epithet) • Hierarchical classification

  5. How is classification achieved? • Observation • Similarities and differences • Fossil record • Molecular analysis • DNA • Ribosomal RNA • Mitochondrial DNA • Proteins

  6. Ideas about classification have changed • Linnaeus- plants and animals (1735) • Where do bacteria and fungi belong? • Von Nägeli- with plants (1857) • Haeckel- Kingdom Protista (1866) • Whitaker – five kingdoms (1969) • Woese- domains (1978)

  7. Classification may change again

  8. Comparison of the three domains

  9. Classification of prokaryotes • Morphology (Gram-staining) • Nutrition • Metabolism • Environmental niche • rRNA sequences (all living cells have them) • Reference: Bergey’s Manual of Systematic Bacteriology; Bergey’s Manual of Determinative Bacteriology) • Most prokaryotes have not been discovered!

  10. Archaea: “extreme bacteria” • Discovered in late 1970’s • Species live at extreme temperature, pH, have unusual metabolic properties • Hard to study

  11. Classification of eukaryotes • Plantae- mosses, ferns, conifers, flworing plants (some algae) • multicellular, photosynthetic • Animalia- sponges, worms, various vertebrates and invertebrates • multicellular, ingest nutrients • Fungi (1959)- yeasts, molds, mushrooms • Absorb nutrients, form hyphae if multicellular • Protists- unicellular organisms • Don’t fit anywhere else!

  12. Classification of viruses • Not cellular, so are not classified in hierarchical system • Viral species- population of viruses with similar characteristics and that occupy a particular ecological niche

  13. Summary • Eukaryotes are much more diverse than prokaryotes • Some have evolved much more recently than others • All are “successful” in their niche • Classification is an ongoing process

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